This MB-1 monoclonal antibody recognizes human CD37. This tetraspanin is expressed on mature B cells, but not on pro-B or plasma cells. CD37 is also weakly expressed on T cells, monocytes, neutrophils, dendritic cells, and macrophages. This cell surface glycoprotein is not detected on NK cells, platelets, or erythrocytes. CD37 is highly expressed on all forms of B cell non-Hodgkin lymphoma, chronic lymphocyte leukemia, and other leukemias. CD37 reportedly associates with MHC class II, CD19, CD21, and other members of the tetraspanin family. CD37 has been implicated in signal transduction, B cell activation, and T cell proliferation. CD37 has been used as a therapeutic target for treating B cell malignancies.